The present invention relates generally to air, smoke and fire dampers, and more particularly, to an operator for use in conjunction with such dampers.
A variety of dampers have been developed for use in regulating the flow of air through a duct system, as well as for use in controlling the passage of fire or smoke through the duct system. Many duct systems are large enough to accommodate relatively large, multiple blade-type dampers, which generally include a plurality of hinged blades disposed within a frame. The damper blades are journalled for rotation within the frame of the damper, so that the blades can be opened or closed as desired. Examples of such dampers may be found, for example, in my U.S. Pat. No. 4,113,230, dated Sept. 12, 1978, and entitled "Rotating Blade Fire Damper"; and my U.S. Pat. No. 4,113,232, dated Sept. 12, 1978, and entitled "Smoke, Fire and Air Control Damper With Stamped Blade".
A variety of damper operators have been developed for use in regulating the positioning of the damper blades between their open and closed position. For example, the damper assemblies previously referred to incorporate an operator which generally comprises a series of brackets attached to each of the blades of the damper, and a connecting rod which is pivotally attached to each of the brackets, so that uniform articulation of the damper blades occurs in response to movement of the connecting rod. Movement of the connecting rod, and accordingly positioning of the damper blades, can then be regulated by any of a variety of control linkages, one example being the linkage shown in my U.S. Pat. No. 4,113,230.
Often, it is important to provide a damper operator which is capable of automatically responding to an external stimulus, such as the smoke or heat of a fire, so that the blades of the damper can be opened or closed, as indicated, both quickly and positively, irrespective of their existing position. One operator which has been developed for this purpose may be found in my U.S. Pat. No. 4,301,569, issued Nov. 24, 1981, entitled "Quadrant Operator". The operator disclosed generally includes a shaft-type actuating means which is selectively interconnected with the connecting rod which is used to regulate movement of the damper blades by a releasing device. The releasing device permits operation of the damper between its open and closed positions during normal conditions, however, upon sensing a selected stimulus, such as heat or smoke, the releasing device is caused to disengage from the connecting rod, so that the damper blades can be urged toward a selected position by an appropriate biasing means.
Such damper operators serve well to properly operate the damper in accordance with the ambient conditions present in the duct system. However, in order to permit the damper blades to be fully rotated between their open and closed position, such damper operators must generally rotate through an arc of approximately 90.degree., so that their rotation will permit full travel of the connecting rod between its terminating positions.
In accordance with the invention disclosed in my prior application Ser. No. 229,830, filed Jan. 30, 1981, a damper is provided with an operator which engages the blade of the damper and causes damper blade rotation during normal operating conditions, when no fire or smoke is detected, but which releases the damper blade, freeing the damper blade for rotation to a selected position, when fire or smoke is detected. To do so, the operator is provided with an articulating assembly which comprises a first arm attached to and extending outwardly transverse to the axis of a drive rod associated with the operator; a second arm, pivoted for rotation with respect to the first arm, having means for engaging the damper blade at one end, and a latch at the other end; and a release mechanism extending between the first arm and the latch of the second arm for selectively latching and releasing the two arms.
During normal operating conditions, the release mechanism is caused to engage the second arm, thus preventing rotation of the second arm with respect to the first arm. As a result, rotational movement of the arms is transmitted to the damper blade, which causes its rotation. Controlled movement of the arms thereby regulates the angular position of the damper blade within the damper opening. In the event that a fire, or other stimulus, is sensed, the release mechanism is caused to disengage from the second arm. This permits the second arm to freely rotate with respect to the first arm. This permits the damper blade to be urged toward a pre-selected orientation (in the case of fire--fully closed) by appropriate biasing means.
In the case of a fire, the air pressure in the side of the duct closest to the fire will normally be greater than the pressure in the duct on the side of the damper most remote from the fire. Accordingly, this differential air pressure tends to force the damper open from its fully closed position. It is desirable therefore to provide a mechanism for resisting the forces on the blade and preventing the blade from opening.